Transcript Sleeping and Dreaming - Hobart and William Smith Colleges

Sleeping and
Dreaming
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Electroencephalogram
(EEG)
Electrodes placed
on scalp provide
gross record of
electrical activity
of brain
EEG :rough index
of psychological
states
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EEG Waves of Wakefulness
Awake, nonattentive
1 second
large, regular
alpha waves
Awake, attentive
1 second
fast, irregular
beta waves
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Stages of Sleep
 Stage 1 - brief
transition stage when
first falling asleep
Sleep stage 1
1 second
Sleep stage 2
 Stages 2 - 4 (slow-wave
sleep) - successively
deeper stages of sleep
 Characterized by
increasing percentage
of slow, irregular, highamplitude delta waves
Spindlers (bursts of activity)
Sleep stage 4
Delta waves
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EEG (De)-Synchronization
 Synchronized activity:
low frequency
high amplitude
 Desynchronized activity:
high frequency
low amplitude
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REM sleep (paradoxical sleep)
Characteristics
EEG waves-irregular, low-amplitude, high
frequency waves (like beta waves)
Postural muscle paralysis
Rapid Eye Movements
genital arousal
irregular heart rate, blood pressure, breathing
Dreams
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Sleep during a typical night
4- 5 cycles; Duration :About 90 minutes
REM sleep takes up increasing amounts of cycle as night
progresses
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Functions of Sleep
Restoration theory
Preservation and protection theory sleep emerged in evolution to preserve
energy and protect during the time of
day when there is little value and
considerable danger
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Sleep Deprivation
Has little effect on performance of
tasks requiring physical skill or
intellectual judgment
Hurts performance on simple, boring
tasks more than challenging ones
Most reliable effect is sleepiness itself
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Dreams and REM Sleep
Everyone dreams several times a night
true dream - vivid, detailed dreams
consisting of sensory and motor
sensations experienced during REM
sleep thought - lacks vivid sensory and
motor sensations, is more similar to
daytime thinking, and occurs during slowwave sleep
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Dreams and REM Sleep
 Function??
 view today : dreams don’t serve any purpose,
but are side effects of REM
 Purpose of REM?
to exercise groups of neurons during sleep?
some are in perceptual and motor areas
 REM rebound: shows significance of REM
 REM occurs in other mammals
 More REM in fetuses and infants
 REM sleep may help consolidate memories
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Circadian Rhythm
Any rhythmic change that continues at
close to a 24-hour cycle in the absence
of 24-hour cues
body temperature
cortisol secretion
sleep and wakefulness
No time cues: cycle becomes longer
than 24 hours
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Brain Mechanisms
Controlling Sleep
 Daily rhythm of sleep and arousal
suprachiasmatic nucleus of the hypothalamus
pineal gland’s secretion of melatonin
 Slow-wave sleep
raphe nuclei of the medulla and pons
secretion of serotonin
 REM sleep
neurons of the pons
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Sleep Disorders
 Somnambulism - sleepwalking
 Nightmares - frightening dreams that wake a
sleeper from REM
 Night terrors - sudden arousal from sleep and
intense fear accompanied by physiological
reactions (e.g., rapid heart rate, perspiration)
that occur during slow-wave sleep
 Narcolepsy - overpowering urge to fall asleep
that may occur while talking or standing up
 Sleep apnea - failure to breathe when asleep
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